[Bug c++/115861] New: ICE: tree check: expected template_decl, have overload in cplus_decl_attributes, at cp/decl2.cc:1896 with deprecated attribute

[iamanonymous.cs at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115861

            Bug ID: 115861
           Summary: ICE: tree check: expected template_decl, have overload
                    in cplus_decl_attributes, at cp/decl2.cc:1896 with
                    deprecated attribute
           Product: gcc
           Version: 15.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: iamanonymous.cs at gmail dot com
  Target Milestone: ---

*******************************************************************************
OS and Platform:
$ uname -a:
Linux 65dac7c84719 4.15.0-213-generic #224-Ubuntu SMP Mon Jun 19 13:30:12 UTC
2023 x86_64 x86_64 x86_64 GNU/Linux
*******************************************************************************
gcc version:
Using built-in specs.
COLLECT_GCC=/home/software/gcc-trunk-3aa004f/bin/gcc
COLLECT_LTO_WRAPPER=/home/software/gcc-trunk-3aa004f/libexec/gcc/x86_64-pc-linux-gnu/15.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../gcc/configure --disable-multilib --disable-bootstrap
--enable-languages=c,c++ --prefix=/home/software/gcc-trunk-3aa004f
--enable-coverage
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 15.0.0 20240630 (experimental) (GCC) 

*******************************************************************************
Program:
$ cat mutant.C
struct { template < a > void b(; __attribute__((deprecated)) friend b<>(

*******************************************************************************
Command Lines:
$ gcc mutant.C
mutant.C:1:30: error: 'a' has not been declared
    1 | struct {          template < a > void b(;               
__attribute__((deprecated)) friend b<>(
      |                              ^
mutant.C:1:41: error: expected identifier before ';' token
    1 | struct {          template < a > void b(;               
__attribute__((deprecated)) friend b<>(
      |                                         ^
mutant.C:1:41: error: expected ')' before ';' token
    1 | struct {          template < a > void b(;               
__attribute__((deprecated)) friend b<>(
      |                                        ~^
      |                                         )
mutant.C:1:97: error: expected identifier at end of input
    1 | struct {          template < a > void b(;               
__attribute__((deprecated)) friend b<>(
      |                                                                        
                        ^
mutant.C:1:97: error: expected ',' or '...' at end of input
mutant.C:1:97: error: expected ')' at end of input
    1 | struct {          template < a > void b(;               
__attribute__((deprecated)) friend b<>(
      |                                                                        
                       ~^
      |                                                                        
                        )
mutant.C:1:93: error: ISO C++ forbids declaration of 'b' with no type
[-fpermissive]
    1 | struct {          template < a > void b(;               
__attribute__((deprecated)) friend b<>(
      |                                                                        
                    ^~~
mutant.C:1:97: internal compiler error: tree check: expected template_decl,
have overload in cplus_decl_attributes, at cp/decl2.cc:1896
    1 | struct {          template < a > void b(;               
__attribute__((deprecated)) friend b<>(
      |                                                                        
                        ^
0x576c1eb diagnostic_context::report_diagnostic(diagnostic_info*)
        ???:0
0x576cabd diagnostic_context::diagnostic_impl(rich_location*,
diagnostic_metadata const*, int, char const*, __va_list_tag (*) [1],
diagnostic_t)
        ???:0
0x578c98b internal_error(char const*, ...)
        ???:0
0x2d6b950 tree_check_failed(tree_node const*, char const*, int, char const*,
...)
        ???:0
0xdca713 tree_check(tree_node*, char const*, int, char const*, tree_code)
        ???:0
0x10731f6 cplus_decl_attributes(tree_node**, tree_node*, int)
        ???:0
0x102cddb grokdeclarator(cp_declarator const*, cp_decl_specifier_seq*,
decl_context, int, tree_node**)
        ???:0
0x106d240 grokfield(cp_declarator const*, cp_decl_specifier_seq*, tree_node*,
bool, tree_node*, tree_node*)
        ???:0
0x1378350 c_parse_file()
        ???:0
0x171c898 c_common_parse_file()
        ???:0
Please submit a full bug report, with preprocessed source (by using
-freport-bug).
Please include the complete backtrace with any bug report.
See <https://gcc.gnu.org/bugs/> for instructions.

Also ICE on trunk.
Compiler Explorer: https://godbolt.org/z/cjYGE3jcP